Sex, how to choose a partner? A switch triggers the attraction!

The scaffold protein Ste5 directly controls a switch-like mating decision in yeast. Evolution has resulted in numerous innovations that allow organisms to increase their fitness by choosing particular mating partners, including secondary sexual characteristics, behavioural patterns, chemical attractants and corresponding sensory mechanisms. The haploid yeast Saccharomyces cerevisiae selects mating partners by interpreting the concentration gradient of pheromone secreted by potential mates through a network of mitogen-activated protein kinase (MAPK) signalling proteins. The mating decision in yeast is an all-or-none, or switch-like, response that allows cells to filter weak pheromone signals, thus avoiding inappropriate commitment to mating by responding only at or above critical concentrations when a mate is sufficiently close. The molecular mechanisms that govern the switch-like mating decision are poorly understood. Here we show that the switching mechanism arises from competition between the MAPK Fus3 and a phosphatase Ptc1 for control of the phosphorylation state of four sites on the scaffold protein Ste5. This competition results in a switch-like dissociation of Fus3 from Ste5 that is necessary to generate the switch-like mating response.

Thus, the decision to mate is made at an early stage in the pheromone pathway and occurs rapidly, perhaps to prevent the loss of the potential mate to competitors. We argue that the architecture of the Fus3–Ste5–Ptc1 circuit generates a novel ultrasensitivity mechanism, which is robust to variations in the concentrations of these proteins. This robustness helps assure that mating can occur despite stochastic or genetic variation between individuals. The role of Ste5 as a direct modulator of a cell-fate decision expands the functional repertoire of scaffold proteins beyond providing specificity and efficiency of information processing5, 6. Similar mechanisms may govern cellular decisions in higher organisms and be disrupted in cancer. Département de Biochimie – Centre Robert-Cedergren, Bio-Informatique et Génomique Université de Montréal, C.P. 6128, Succursale centre-ville Montréal, Québec H3C 3J7, Canada – Department of Mathematics, Imperial College London, South Kensington Campus, London SW7 2AZ, UK – Department of Physiology, McGill University, 3655 Promenade Sir William Osler, Montréal, Québec H3G 1Y6, Canada – Centre for Systems Biology at Edinburgh, University of Edinburgh, Edinburgh EH9 3JD, UK – These authors contributed equally to this work. news from nature.com ~ Sexual attraction; Sexual attractiveness or sex appeal refers to a person’s ability to attract in a sexual or erotic manner the interest of another person. The attraction may be

to a physical quality of a person, or to other, more amorphous qualities of the person.Though attempts have been made to devise objective criteria of sexual attractiveness, a person’s sexual attractiveness is to a large extent a subjective measure dependent on another person’s interest, perception and sexual orientation. For example, a gay or lesbian person would typically find a person of the same sex to be more attractive than one of the other gender. A bisexual person would often find both sexes to be attractive. Asexuality refers to those who do not experience sexual attraction for either sex, though they may have romantic attraction (homoromantic, biromantic or heteroromantic).Human sexuality has many aspects. In biology, sexuality describes the reproductive mechanism as well as the basic biological drive that exists in all species and can encompass sexual intercourse and sexual contact in all its forms. There are also emotional and physical aspects of sexuality. These relate to the bond that exists between individuals, which may be expressed through profound feelings or emotions. Sociologically, it can cover the cultural, political, and legal aspects; and philosophically, it can span the moral, ethical, theological, spiritual or religious aspects.Which aspects of a person’s sexuality attracts another is influenced by cultural factors, and has varied over time, as well as personal factors. Influencing factors may be determined more locally among sub-cultures, across sexual fields, or simply by the preferences of the

individual. These preferences come about as a result of a complex variety of genetic, psychological, and cultural factors. A person’s physical appearance has a critical impact on their sexual attractiveness. This involves the impact one’s appearance has on the senses, especially in the beginning of a relationship: * Visual perception (how the other looks and acts); * Audition (how the other’s voice and/or movements sound). * Olfaction (how the other smells, naturally or artificially; the wrong smell may be repellent); As with other animals, pheromones may also have an impact, though less significantly in the case of humans. Theoretically, the “wrong” pheromone may cause someone to be disliked, even when they would otherwise appear attractive. Frequently a pleasant smelling perfume is used to encourage the member of the opposite sex to more deeply inhale the air surrounding its wearer[citation needed], increasing the probability that the pheromones from the individual will also be inhaled. The importance of pheromones in human relationships is probably limited and is widely disputed, although it appears to have some scientific basis.Many people exhibit high levels of sexual fetishism, and are sexually stimulated by other stimuli not normally associated with sexual arousal. The degree to which such fetishism exists or has existed in different cultures is controversial. ~ GoodNews International

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